Polyarylene sulfides are high-performance polymers that may withstand high thermal, chemical, and mechanical stresses and are beneficially utilized in a wide variety of applications. Polyarylene sulfides are generally formed via polymerization of a dihaloaromatic monomer with an alkali metal sulfide or an alkali metal hydrosulfide in an organic amide solvent.
Following formation, polyarylene sulfides can be subjected to a crystallization process that can affect optical, mechanical, thermal, and/or chemical properties of the polymer. While crystallization methods can be carried out according to several different processes (e.g., stretching), it is common for polyarylene sulfides to be crystallized upon cooling from the melt, for instance following final polymerization during a formation process. Unfortunately, even minor variations in the crystallization process can lead to large differences in the degree of crystallization of the polymer and as such large variation in the polymer characteristics. Accordingly, crystallization processes must be tightly controlled so as to avoid such variations.
Methods have been developed to improve control of the cooling crystallization of the formed polymers, and thus improve the desired qualities of the semi-crystalline polyarylene sulfide product. For instance, the use of temperature controlled jacketing around a reactor to maintain a temperature differential between the jacketing and the polymer through a slow cooling process has proven useful.
While such cooling crystallization processes have been developed and improved upon to better control the crystallization of polyarylene sulfides, room for further improvement exists. What is needed in the art is a method and system for crystallization of polyarylene sulfides that can provide reliable and consistent crystallization. Such improvements can be utilized to provide polyarylene sulfides with more consistent characteristics.